Foundations and Applications

Gilbert N. Lewis

AMERICAN PHYSICAL CHEMIST
1875–1946

Gilbert Newton Lewis was born on October 25, 1875, in West Newton,
Massachusetts. A precocious child, he received his early education at home
and learned to read by the age of three. When Lewis was nine, his family
moved to Lincoln, Nebraska. He attended the University of Nebraska for two
years and in 1893 transferred to Harvard University, from which he
received his B.S. in 1896.

After a brief stint as a teacher at Phillips Academy in Andover,
Massachusetts, Lewis returned to Harvard, where he obtained his M.A. in
1898 and Ph.D. in 1899. He subsequently studied at the universities at
Göttingen and Leipzig in Germany (1900–1901) and then
returned to Harvard as an instructor (1901–1906). In 1907 Lewis
became an assistant professor at the Massachusetts Institute of
Technology, where he soon rose to the rank of full professor.

American chemist Gilbert N. Lewis, a theorist of chemical bonds, or
valence.

In 1912 Lewis accepted a position as dean and chairman of the College of
Chemistry at the University of California, Berkeley. He remained at
Berkeley for the rest of his life and transformed the chemistry department
there into a world-class center for research and teaching. His reforms in
the way chemistry was taught, a
catalyst
for the modernization of chemical education, were widely adopted
throughout the United States. Lewis introduced thermodynamics to the
curriculum, and his book on the same subject became a classic. He also
brought to the study of physical chemistry such concepts as fugacity,
activity and the activity coefficient, and ionic strength.

At the beginning of the twentieth century physicists tried to relate the
electronic structure of atoms to two basic chemical phenomena: the
chemical bond (the
attraction
between atoms in a molecule) and
valence
(the quality that determines the number of atoms and groups with which
any single atom or group will unite chemically and also expresses this
ability to combine relative to the hydrogen atom). German chemist Richard
Abegg was the first to recognize in print the stability of the group of
eight electrons, the arrangement of outer electrons that occurs in
noble gases
and is often attained when atoms lose or gain electrons to form ions.
Lewis called this the "group of eight," and American chemist
and physicist Irving Langmuir labeled it an "octet."

In 1902, while explaining the laws of valence to his students at Harvard,
Lewis conceived a concrete model for this process, something Abegg had not
done. He proposed that atoms were composed of a concentric series of cubes
with electrons at each of the resulting eight corners. This "cubic
atom" explained the cycle of eight elements in the Periodic Table
and corresponded to the idea that chemical bonds were formed by the
transfer of electrons so each atom had a complete set of eight electrons.
Lewis did not publish his theory, but fourteen years later it became an
important part of his theory on the shared electron-pair bond.

In 1913 Lewis and Berkeley colleague William C. Bray proposed a theory of
valence that differentiated two different types of bond: a polar bond
formed by the transfer of electrons and a
nonpolar
bond not involving electron transfer. In 1916 Lewis published his seminal
article suggesting that the chemical bond is a pair of electrons shared or
held jointly by two atoms. He depicted a single bond by two cubes sharing
an edge, or more simply by double dots in what has become known as Lewis
dot structure.

According to Lewis's octet rule, each atom should be surrounded by
four pairs of electrons, either shared or free pairs. Lewis derived
structures for
halogen
molecules, the ammonium ion, and oxy acids, inexplicable according to
previous valence theories. He viewed polar bonds as unequally shared
electron pairs. Because the complete transfer of electrons was only an
extreme case of polarity, he abandoned his earlier dualistic view; the
polar theory was just a special case of his more general theory.

Lewis's shared electron-pair theory languished until Langmuir
revived and elaborated it beginning in 1919. It was soon accepted as the
Lewis–Langmuir theory, one of the most fundamental concepts in the
history of chemistry.

Lewis's acid-base concept is also well known to introductory-level
chemistry students. A Lewis acid, for example, BF
3
, AlCl
3
, or SO
3
, is a substance
that can accept a pair of electrons from a Lewis base, for example, NH
3
or OH−, which is a substance that can donate a pair of electrons.
It can be applied to various areas, for example,
coordination chemistry
: The metal ion is a Lewis acid, the
ligand
is a Lewis base, and the resulting formation of a
coordinate covalent bond
corresponds to a Lewis acid–base reaction.

Lewis made additional valuable contributions to the theory of colored
substances, radiation, relativity, the separation of
isotopes
, heavy water, photochemistry, phosphorescence, and fluorescence. As a
major in the U.S. Army Chemical Warfare Service during World War I, he
worked on defense systems against poison gases. From 1922 to 1935 he was
nominated numerous times for the Nobel Prize in chemistry. Lewis's
death, while measuring the dielectric constant of hydrogen cyanide on
March 23, 1946, precluded his receiving the prize, which is not awarded
posthumously.